20 CFR § 404.366 - “Contributions for support,” “one-half support,” and “living with” the insured defined - determining first month of entitlement.
To be eligible for child's or parent's benefits, and in certain Government pension offset cases, you must be dependent upon the insured person at a particular time or be assumed dependent upon him or her. What it means to be a dependent child is explained in §§ 404.360 through 404.365; what it means to be a dependent parent is explained in § 404.370(f); and the Government pension offset is explained in § 404.408a. Your dependency upon the insured person may be based upon whether at a specified time you were receiving contributions for your support or one-half of your support from the insured person, or whether you were living with him or her. These terms are defined in paragraphs (a) through (c) of this section.
(a) Contributions for support. The insured makes a contribution for your support if the following conditions are met:
(1) The insured gives some of his or her own cash or goods to help support you. Support includes food, shelter, routine medical care, and other ordinary and customary items needed for your maintenance. The value of any goods the insured contributes is the same as the cost of the goods when he or she gave them for your support. If the insured provides services for you that would otherwise have to be paid for, the cash value of his or her services may be considered a contribution for your support. An example of this would be work the insured does to repair your home. The insured person is making a contribution for your support if you receive an allotment, allowance, or benefit based upon his or her military pay, veterans' pension or compensation, or social security earnings.
(2) Contributions must be made regularly and must be large enough to meet an important part of your ordinary living costs. Ordinary living costs are the costs for your food, shelter, routine medical care, and similar necessities. If the insured person only provides gifts or donations once in a while for special purposes, they will not be considered contributions for your support. Although the insured's contributions must be made on a regular basis, temporary interruptions caused by circumstances beyond the insured person's control, such as illness or unemployment, will be disregarded unless during this interruption someone else takes over responsibility for supporting you on a permanent basis.
(b) One-half support. The insured person provides one-half of your support if he or she makes regular contributions for your ordinary living costs; the amount of these contributions equals or exceeds one-half of your ordinary living costs; and any income (from sources other than the insured person) you have available for support purposes is one-half or less of your ordinary living costs. We will consider any income which is available to you for your support whether or not that income is actually used for your ordinary living costs. Ordinary living costs are the costs for your food, shelter, routine medical care, and similar necessities. A contribution may be in cash, goods, or services. The insured is not providing at least one-half of your support unless he or she has done so for a reasonable period of time. Ordinarily we consider a reasonable period to be the 12-month period immediately preceding the time when the one-half support requirement must be met under the rules in §§ 404.362(c)(1) and 404.363 (for child's benefits), in § 404.370(f) (for parent's benefits) and in § 404.408a(c) (for benefits where the Government pension offset may be applied). A shorter period will be considered reasonable under the following circumstances:
(1) At some point within the 12-month period, the insured either begins or stops providing at least one-half of your support on a permanent basis and this is a change in the way you had been supported up to then. In these circumstances, the time from the change up to the end of the 12-month period will be considered a reasonable period, unless paragraph (b)(2) of this section applies. The change in your source of support must be permanent and not temporary. Changes caused by seasonal employment or customary visits to the insured's home are considered temporary.
(2) The insured provided one-half or more of your support for at least 3 months of the 12-month period, but was forced to stop or reduce contributions because of circumstances beyond his or her control, such as illness or unemployment, and no one else took over the responsibility for providing at least one-half of your support on a permanent basis. Any support you received from a public assistance program is not considered as a taking over of responsibility for your support by someone else. Under these circumstances, a reasonable period is that part of the 12-month period before the insured was forced to reduce or stop providing at least one-half of your support.
(c) “Living with” the insured. You are living with the insured if you ordinarily live in the same home with the insured and he or she is exercising, or has the right to exercise, parental control and authority over your activities. You are living with the insured during temporary separations if you and the insured expect to live together in the same place after the separation. Temporary separations may include the insured's absence because of active military service or imprisonment if he or she still exercises parental control and authority. However, you are not considered to be living with the insured if you are in active military service or in prison. If living with is used to establish dependency for your eligibility to child's benefits and the date your application is filed is used for establishing the point for determining dependency, you must have been living with the insured throughout the month your application is filed in order to be entitled to benefits for that month.
(d) Determining first month of entitlement. In evaluating whether dependency is established under paragraph (a), (b), or (c) of this section, for purposes of determining whether the conditions of entitlement are met throughout the first month as stated in § 404.352(a)(2)(i), we will not use the temporary separation or temporary interruption rules.